What is an adverse inference in Ontario litigation?

An adverse inference is a conclusion that a court is permitted to draw against a party who fails to produce evidence that they could reasonably be expected to have available. In Ontario litigation, an adverse inference can be requested when a party destroys relevant documents, fails to call a witness who logically would support their case, or deliberately withholds evidence without proper justification.

The classic situation is spoliation — intentional or negligent destruction of relevant evidence. If a party destroys documents after reasonably anticipating litigation, the court may instruct itself (or a jury, in jury trials) that the destroyed evidence would have been unfavorable to the party who destroyed it. This can be a devastating inference in a closely contested case.

An adverse inference can also be sought when a party fails to call a witness who is uniquely within their knowledge or control and whose evidence would logically be material. The court may infer that the reason the witness was not called is that their evidence would have hurt the party who controlled them. Courts apply adverse inferences judiciously — there must be a reasonable basis for the request, and the court has discretion about whether to draw the inference and how much weight to give it. This is why evidence preservation from the earliest stages of a dispute is so critical.